Preparation of tetrachlorothiophene



Patented Dec. 27, 1949 PREPARATION OF TETRACHLORO- THIOPHENE 7 Harry L. Coonradt, Woodbury, and Howard D.

Hartough, Pitman, N. J., assignors to Socony- Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application February 18, 1947, Serial No. 729,410

This invention relates to a new process for preparing tetrachlorothiophene.

This compound has heretofore been prepared principally by the direct chlorination of thiophene at room temperature and subsequent isolation of the desired compound from the resulting crude thiophene-chlorine reaction mixture.v

The direct reaction between thiophene and chlorine proceeds easily and rapidly under normal conditions to yield a mixture comprising unreacted thiophene, monochlorothiophene, dichlorothiophene, trichlorothiophene, tetrachlorothiophene and chlorine addition products of thiophene.

To obtain a clear-cut separation of the various chlorothiophenes, the method developed over sixty years ago, and accredited to Victor Meyer, has heretofore generally been employed. This method involves heating the crude chlorination reaction mixture with alcoholic potassium hydroxide for several hours to destroy addition products formed during the course of reaction, followed by addition of water and subsequent steam distillation and fractionation of the mixture so obtained to yield the various chlorothiophenes.

The yields of tetrachlorothiophene obtained in accordance with the above described procedure have been small and the process has certain inherent disadvantages which render it inapplicable for the production of this compound in commercial quantities. Foremost of these disadvantages is the excessively long heating time of the crude chlorinated thiophene mixture with alcoholic potassium hydroxide. Under ordinary conditions of chlorination, the resulting thiophene-chlorine reaction mixture frequently requires a heating period with alcoholic potassium hydroxide of the order of one day or longer in order to insure the complete removal of addition products therefrom. Thus, the process heretofore used for obtaining tetrachlorothiophene has been a slow time-consuming operation and yields of resultant product have been comparatively small.

In addition to being a slow, drawn-out procedure, the aforementioned process is unattractive from an economical point of view, when carried out on a commercial basis, since the loss of alcohol or the expense of recovering alcohol from the spent potassium hydroxide solution would greatly increase theoverall cost of production. Furthermore, the excessive amount of fuel consumed during the extended heating period of the thiophene-chlorine reaction mixture 6 Claims. '(Cl. 260329) course, not to be limited by any theory, it is with alcoholic potassium hydroxide and the labor costs which would be involved in said period render the process totally inadequate as an efficientmethod for producing tetrachlorothiophene.

In accordance with the present invention, there has now been discovered a method of preparing; tetrachlorothiophene which tends to overcome the disadvantages inherent in the process heretofore employed. Broadly stated, the process contemplated herein comprises chlorinating thiophene with chlorine and subsequently maintaining the reaction mixture at an elevated temperature while passing an excess of chlorine through the same for a period of time sufiicient to destroy substantially all of the chlorine or hydrogen chloride addition products produced during the course of reaction and contained in the chlorinated mix-, ture.

It has been established that when thiophene is brought into contact with an excess of chlorine, the principal product resulting is a thiophene-chlorine addition product such as the hex-4 achlorothiolane described more completely in copending application SerialNumber 747,327, filed May 10, 1947. While the present invention is, of

': believed that upon carrying out the chlorination of thiophene under conditions similar to those required to obtain addition products of the nature of hexachlorothiolane, and then maintaining the tion products produced during the aforesaid chlorination are decomposed to yield a product which,

upon fractionation, produces a substantial yield According to the pref-- of tetrachlorothiophene. erable procedure of this invention, chlorine gas will be added to the chlorinated reaction mix-' ture while the same is maintained at an elevated temperature.

It has been foundthat by carrying out the method in comparison with the timeeconsuming process of the prior art. Moreover, the method of this invention is a simple procedure for preparing tetrachlorothiophenecwhich permits higher yields of this compound tobeobtained-andthis, in turn, causes a substantial reduction in the expenditure required per unit of tetrachlorothiophene obtained and hence gives 1i$Q-tQia highly economical and efiicient method of pm:-

duction.

It is accordingly an object of the present invention to provide an efiective process for pre paring -tetraclorothiophene wherein the extensive heating-period necessary to theprior art procedure can-be substantially reduced-to provide a comparativelyrapid; eficient process. A'still further object is "toafiord aprocess -forobtaining tetrachlorothiophene ina--hi gher-yield than heretofore obtained. Awery-important b3'ec-t is the provision of an economical --methodfor makingtetrachlorothiophene which requires less apparatus andattention than-has been necessary in--the prior -art--procedure.-

These and other-objects which will 'be recognized by those -sli1-ledin -the --a-rt-are attained inaccorda'nce with-the present invention; wherein tetrachlorothiophene is prepared by" contacting thiophene witlrat leastabout 4 moles of chlorine per mole of thiophene and thereafter maintaining the thiophene-chlorine reaction ,mixture, while passing additiona l 'chlgrine therethrough, at an elevatedjtfim erature for a period of time fioiont. t dec mpose. Substan i lly a of t on roducts esultin in the. a oresa d hlo na iono the. neat-t eate V dyields trach1orothiophene tia Lyie dLa Qne wi h. th r v able hlorin d thio heneproducts. h r ue rewltinniromna ra tiona ion o s ts lar e y of. a orn o nd. identifi d 134 -3W5 ex cl lor o 2.2 di;thienyl. This compound. is isolated y.- crys allizatio .oithorosid e;

Th tem ratur at. wh c c l r at f h ophene arr ed out acc rda ce w the roces of this nv ntio. may b betwe n a t ondnhont. 200 Gc cra yg-howe e t e.

emp ature i b maintained betw en about 0 d' abo t 0.0? C. s nce fitzhas .been un a e lo i ati n pr oeeds w th. reat a to produce increased yieldspi the desired prodno in. the-hig r tem ature ra ge. o effect h o n ricl arv rat o ofoh or e to thiophene o a eotaho tel;.and re erably higher is. employed,

he hl ination-wil pre era ly-ho oa r edoutunder-reflux, {Ih phone at. atn10$ bou 8039.- As hv eeds y thezad Q i ti mnerntn :o ch

orination rea tion. pro: .ohl rine to the. thio+ phon 1 the emi rate oiwrt e. reacti n rn tu e ses: h -chlorination mayrbeecarried out, in.

y uit b e :manner ho sin t e. t iophe e nd.

p iers r -W: -l hence e temperature of the reaction mixture under such conditions will not generally rise above about 200 C. At the completion of the chlorination reaction, the resulting mixture is maintained at an elevated-temperature ator above :refiux for a period of-'time suflicient*to--decompose chlorine or hydrogen chloride addition products produced during the course of chlorination. The temperature during-this period will generally be between about C. and about 200 C., and preferably chlorine gas is passed through the chlorinatedmixture while the same is maintained in--thealcovedzen' perature range. This period of heating may extend from comparatively few minutes to several hours and will generally be between.about-;5;n1inutes and about 5 hours, depending upon the extent of chlorination and the temperature at which said chlorination was effected. As a general rule, it has been found that relatively shorter heating periods .are required when the chlorination is carried out'at the higher temperatures.-

The af sa d heat n of t eaction. mixture resultingupon chlorination is an essential, step.

the process of thi invention. Merely con-r aotinst iophene with-Jan excess of h1or ne,-.

en t elevat d em erature, was n t s m cient in itself, as will be shown below, to in:

w en nose oimwlmmra inert-g s s so .e n-

' plo edt. Theheatinsp the chl rinated mi ture. lns l y be carr ed-out a at o p eric-p es ur nough un er. nome cond t ons 7 it may be desirabl o employ pre sure/si e.

ld the obyv etob a nehen-t ns rres ondin ly reduced.

igher; I"

h v er d.

shaman rterzminatin mating before the;

dditionimrodncts a resent inzlthesreaction ,mixe. tureiaregcompletely decomposed and. readily res moving the remaining addition products-:pres. ent by :the addition. of z 'a-.'smal1 amount of alkali.

The :amountof; alkaline material necessary under such. conditions -is--only -a-fraction-'-of that required in the procedure-'of-preparing tetrachloro-- thiophene -aspracticed heretoiore and the yieldof product is substantially higher; Any of the commonlyemployed-alkaline -materials may be used for this purpose. Generally anaqueous solution-of a-hydroxide or;carbonate of the alkali metals or alkaline "earth"metals or a solid alkali willbe used: At the completion ofythe heating; period the chlorinated," mixture is, fractionated.

usually under reduced pressure to give asubstantial yield of tetrachlorothiophene.

he followi snxa n les il serve oi lu tr h pr ce of thi xin e t on without im ng. e some:

Example 1 om: we rinat and -.heno.e;

t. e in-t e-ranseon Q1: u in 5011c :r-emainderaof ichloenst mix une'sbecame eheatedio. ;a stem, ose oaloont 23: (3. durin he: o o the-reac on. .Atth comnletion-of-the. chlorination; A the reaction --;mixtur.e. was mfilnrztamed zatnrefiuxutemnerature and-20.. additional.

Weight Per Cent of Total Product Trichlorothiophene Tetrachlorothiophene Hexa chlorodithienyl.

gigh Boilers.

Example 2 Thirty-five moles of thiophene were chlorinated with 140 moles of gaseous chlorine. The mixture was cooled during addition of the first moles of chlorine, maintaining a temperature of about C. During the remainer of the chlorination, the mixture was heated at reflux temperature, which rose to about 190 C. during the course of the reaction. At the completion of the chlorination, the reaction mixture was kept at a. temperature of 185 C. and a small stream of nitrogen was passed through it for 2 /2 hours. The mixture was then washed with water and fractionated under reduced pressure to give the following:

Weight Per Product Cent of Total Example 3 Ten moles of thiophene were chlorinated with 89 moles of chlorine. The mixture was heated and the temperature during the chlorination was maintained at the reflux temperature of the mixture, rising from about 80 C. at the beginning of the reaction to about 188 C. at the end of the reaction. A stream of nitrogen was passed through the hot reaction mixture maintained at a temperature of 185 C. for a period of 3 hours. The mixture so treated was then cooled, washed successively with water, a 5 per cent by weight aqueous solution of sodium carbonate and water,

Example 4 Ten moles of thiophene were chlorinated with 68 moles of gaseous chlorine. The mixture was heated and the temperature held between C. and C. during the reaction. The reaction mixture was washed successively with water, a

5 per cent by weight aqueous solution of sodium carbonate, a 5 per cent by weight aqueous solution of thiosulfate, a 5 per cent by weight aqueous solution of sodium carbonate and water. The mixture was then dried over sodium sulfate and fractionated under reduced pressure to give the following:

Weight Product Per Cent of Total Dichlorothiophene 0. 7 Trichlorothiophene 4. 5 Tetrachlorothiophene. 3. 3 Hexachlorothiolane. 80. 2

High Boilers 5. 9 Residue l 2. 9 Loss 2. 5

The above results indicate that more chlorination of thiophene at an elevated temperature does not give the substantial yields of tetrachlorothiophene obtained in accordance with the process of this invention but that subsequent heating of the chlorinated mixture is apparently an essential factor in the present process.

We claim:

1. A process for preparing tetrachlorothiophene, which comprises reacting thiophene with an excess of chlorine present in an amount greater than about four moles per mole of thiophene, subjecting the reaction mixture resulting from the aforesaid chlorination to an elevated temperature above the boiling point of thiophene while passing chlorine gas through the same for a period of time suflicient to decompose substantially all of the thiophene-chlorine addition products produced during the course of said reaction and thereafter fractionally distilling the heat-treated chlorinated mixture to yield tetrachlorothiophene.

2. A process for preparing tetrachlorothiophene, which comprises reacting thiophene with an excess of chlorine present in an amount greater than about four moles er mole of thiophene,

subjecting the reaction mixture resulting from the aforesaid chlorination to an elevated temperature between about 80 C. and about 200 C. while passing chlorine gas through the same for a period of time sufficient to decompose substantially all of the thiophene-chlorine addition products produced during the course of said reaction and thereafter fractionally distilling the heattreated chlorinated mixture to yield tetrachlorothiophene.

3. A process for preparing tetrachlorothiophene, which comprises reacting thiophene under reflux with at least about four moles of chlorine per mole of thiophene, subjecting the reaction mixture resulting from the aforesaid chlorination to an elevated temperature between about 80 C. and about 200 C. While passing chlorine gas through the same for a period of time sufficient to decompose substantially all of the thiophene-chlorine addition products produced during the course of said reaction and thereafter fractionally distilling the heat-treated chlorinated mixture to yield tetrachlorothiophene.

4. A process for preparing tetrachlorothiophene, which comprises reacting thiophene under 7? reflux with at least QbQRtLfOl-lli moles of chlorine per mole, of, thiophene, subjecting the. reaction mixture resulting. from the aforesaidfchlorination tolanelevated temperature between about80C." andabout' 200 C; while passing chlorine gas through the same, for aperiod'; of time sufli'cient to decompose a substantial proportion of the thiophene-chlorine addition products produced during the courseofsaid reaction, treating the chlorinated mixture '50 obtained with an alkaline. material'toremove remaining thiophene-chiorine addition" products and fractionaliy distilling to yield t'etrachlorothibphene:

5. A process for preparing tetrachlorothiophene, which comprises reacting thiophene with atileastabout four moles of chlorine per mole of thiophene at a temperature between about 80 C. and I about 200 C., subjecting the reactionmixture resulting from the aforesaid chlorinationzto: anrelevatedtemperature between about-SOFCLandI about 200 C. while passing. chlorineigaathroughi the same fora period of time sufficient'to'decom r pose a substantialproportion of,.the. thiophene-s chlorine addition products produced during the courses of. saidrv-reaction, treating the chlorinated mixture. so. obtainedswithz alkalito. remove re maining; thiopheneqchlorine, addition. products, L; and fractionallyidistillinggto igielditetrachlorothig phene.

6; A processgzforzpreparing, tetrachlorothiovphenewhich comprises reacting thiophenewith aniexcessof chlorine present in'an amountgreater; than about-four moles pep molerof .thiophene,

subjectii-ig thereaction-.mixture resulting from. the aforesaidrchlorination :to-,an -,elevated, temper-.-

REFERENCES CITED The following references-are of record in the file; of; this pateniki,

Ber. 19; 65011886); 

